The Bronze and the Pale: Why Some Skin Doesn't Tan

by
Vanessa Day

In the warm summer months, people spend more and more time outside. The minute the temperature climbs, people shed the layers and expose their skin to the sun’s rays. But while some will notice darker skin within hours of being outdoors, others may struggle to achieve that golden tan. So, why do some people tan more than others under the same conditions? Well, not surprisingly, it has a lot to do with out ancestors. A recent study from two anthropology professors at Penn State University revealed that the reason some skin tans more than others is in direct relation to where our relatives chose to live.

The As, Bs, and Ds of Tanning

It’s a known fact that people from tropical climates have darker skin, but how and why did that skin pigmentation evolve? It all has to do with the variation of ultraviolet radiation around the world. After studying UVA and UVB rays at different latitudes, the professors found that UVB was more intense near the equator and less intense further away. UVB rays produce vitamin D in skin, but it can also destroy folate, which is essential in the growth of cells. In order to protect themselves from sun damage, our ancestors had to adapt, and tanning evolved as the solution.

When humans were mainly living in tropical regions, where both UVA and UVB rays are high year-round, their skin naturally became darker to protect them from the harsh sunbeams. The dark pigmentation prevented folate destruction while still allowing some vitamin D production. But as our ancestors migrated away from the equator into the subtropics and up to the artic areas, where UVB radiation is not consistent or strong enough all the time to produce vitamin D, populations evolved to have light pigmentation. This allowed for more vitamin D production in areas where the sun does not shine as often or as intensely.

As a result, the northern regions of the world, like Canada, Russia, Scandinavia and Western Europe, have produced pale-skinned individuals that are less likely to develop a tan. The areas of North Africa, South America and the Mediterranean engendered dark-pigmented people capable of acquiring that summer glow.

Sun Exposure Determines Tanning Ability

Through the years, the tanning process has evolved to help protect our skin from too much sun exposure. For some that means a nice, dark tan by summer’s end, while others may suffer painful sunburns and constant pale skin. The good news is the reason your skin won’t tan is not your fault, it’s just in your genes.

But whether you hail from the fairer regions of the north or the golden latitudes near the equator, it’s important to understand the effects of tanning and how to keep yourself safe. Taking precautions like wearing protective clothing, applying sunscreen and limiting your time in direct sunlight are essential to keeping your skin youthful and healthy.